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Non-contact positive dispense solid powder sampling apparatus and method

Non-contact positive dispense solid powder sampling apparatus and method description/claims

This application claims the benefit of U.S. Provisional Application Ser. No. 60/897,688, filed Jan. 26, 2007, the entirety of which is hereby incorporated by reference herein.

1. Field of the Invention

The invention relates generally to solid handling or manipulating and, more particularly, to systems and methods of solid powder sampling or aspirating and non-contact delivery or dispensing of small amounts of dry powders or solids.

2. Description of the Related Art

There continues to be an increase in demand for the discovery, development and optimization of new materials. These new materials cover the range from polymers, adhesives, and pharmaceuticals all the way to catalysts, phosphors and semiconductors, among others.

A variety of methods and devices exist for obtaining and dispensing small amounts of liquids that have found use in a variety of applications. However, few methods and devices exist for accurately, precisely and/or efficiently manipulating small amounts of solids (e.g., powders), for example, in the milligram range or lower. In the laboratory, such small amounts of solids are often dispensed by hand using a scale. Unfortunately, such methods are not amenable to the rapid or automated manipulation of compounds, as they are tedious, time consuming, and prone to error.

This disadvantageously not only reduces process efficiency but also undesirably adds to the cost. Moreover, it is a difficult task to effectively utilize small quantities of solids, such as powders, when complex steps to precisely handle, transfer, deliver and process such small quantities are entailed.

Certain embodiments provide novel and/or improved systems and methods for non-contact positive dispense solid powder handling and/or manipulation. Some embodiments advantageously provide the ability to pick up powders at either constant displacement (e.g., known powder depth) or constant pressure (e.g., powder height independent), thereby desirably providing enhanced versatility and options. In some embodiments, motorized aspiration (e.g., allows for variable fill height) is utilized in combination with pneumatic dispense (e.g., can permit better powder ejection). Again, this desirably permits flexible and optimized operation.

In accordance with some embodiments, a powder handling system is provided. The powder handling system generally comprises a dispense head which comprises at least one channel for sampling and delivering a powder. The channel comprises a probe that is at least partially insertable into a powder source to sample a predetermined amount of the powder and dispense the predetermined amount of the powder into or onto a target. The dispense head is configured such that it can be selectively operated such that the probe has the ability to pick up the powder in either a constant displacement mode with a known powder depth or a constant pressure mode which is substantially independent of powder height.

In some powder handling embodiments, the dispense head is moveable by a pneumatic or motor driven actuator. In some powder handling embodiments, the probe comprises a moveable plunger housed within an outer tube. In some powder handling embodiments, the powder source comprises a vial which is positioned in a holder assembly which comprises a vibration device that facilitates in settling the powder in the vial after a sampling operation. In some embodiments, this holder assembly further comprises a flexible stripper plate that facilitates in removal of any powder that may adhere to the probe outer surface during a sampling operation. In some powder handling embodiments, the probe is displaceable in a shearing, motion to facilitate removal of any excess powder extruding from a distal orifice of the probe. In some powder handling embodiments, the probe size is selectable from a range of different probe sizes. In some powder handling embodiments, the system comprises a reflective sensor. In some powder handling embodiments, the system comprises a proximity sensor. In some powder handling embodiments, the system comprises a controller. In some powder handling embodiments, the system comprises a motion control system. In some powder handling embodiments, the system can sample from a powder source containing as low as 1 milligram or less of the powder. In some powder handling embodiments, the system can dispense powder in the microgram range. In some powder handling embodiments, the powder comprises particles having a size in the range from about 5 microns (μm) to about 10 microns (μ). In some powder handling embodiments, the powder comprises particles having a size in the range from about 100 microns (μm) to about 150 microns (μm).

In accordance with some embodiments, a method of handling a powder is provided. The method generally comprises inserting a probe in a source containing a powder to be sampled and delivered to a target, and selecting between two modes of powder sampling. A first mode of the two modes comprises picking up the powder in a constant displacement mode with a known powder depth. A second mode of the two modes comprises picking up the powder in a constant pressure mode which is substantially independent of powder height. A predetermined amount of the powder is sampled by one of the first or second modes and a predetermined quantity of the powder is delivered to the target.

In some powder handling embodiments, a plunger of the probe is used to compress the powder prior to the sampling of said powder. In some embodiments, the compression force exerted by this plunger is measured. In some embodiments, this compression force is measured by a force or pressure sensor. In some powder handling embodiments, the delivery of a predetermined quantity of the powder to the target comprises pneumatically dispensing the powder. In some powder handling embodiments, the delivery of a predetermined quantity of the powder to the target comprises dispensing the powder using a motorized actuator. In some powder handling embodiments, the predetermined amount sampled and the predetermined quantity delivered are substantially the same. In some powder handling embodiments, the predetermined amount sampled is greater than the predetermined quantity delivered. In some powder handling embodiments, the mass of the powder delivered to the target is measured. In some embodiments, this mass measurement comprises using a mass balance or load cell to perform the mass measurement. In some powder handling embodiments, the mass of powder in the source is in the range from about 5 milligrams (mg) to about 50 milligrams (mg). In some powder handling embodiments, the mass of powder delivered to the target is in the range from about 100 micrograms (μg) milligrams to about 20 milligrams (mg).

Some embodiments of the invention relate to automated dispensing of small amounts of dry powder or solids. The amount delivered can vary from the order of nanograms to milligrams or more. Some embodiments are based on filling a cavity of known, but adjustable, volume, followed by positive displacement or ejection.

In some embodiments, a sample probe is used to dispense powders. A variety of different probe sizes can be provided with efficacy, as needed or desired. The sample probe, in some embodiments, comprises a generally cylindrical needle with a movable plunger. This sample probe advantageously allows for the ability to sample directly from source vessels, without the need to pre-process the powder. This is one unique feature of certain embodiments the system and it allows for use in applications where sampling from native source vessels is desired or required. Moreover, embodiments of the invention allow for sampling from sample masses which can be as low as 1 milligram or less.

This low mass sampling feature of embodiments of the invention is unmatched by most, if not all, conventional technologies used for delivering dry powders including those that rely on either mechanical means such as vibratory hoppers or on vacuum aspiration.

In some embodiments, each dispensing probe desirably has a substantially fixed diameter and a movable plunger. This movable plunger allows a fill height to be programmed. This fill height, combined with the fixed probe diameter yields a volume or cavity to be filled. Based on a particular powder's bulk density this volume will contain a specific mass of material. Clearly this mass can be changed by corresponding changes in the fill height (e.g., by moving the plunger).

Because powders have widely varying properties in terms of compressibility, cohesiveness, flowability, among others, several process procedures related to embodiments of the invention have been developed. Because the plunger, in some embodiments, is attached to an independent actuator (e.g., an electric motor drive), the ability to “compress” the powder against either the powder bed or the vessel bottom is gained. This compression advantageously allows for highly flowable and/or non-cohesive powders to be handled, and allows for enhanced powder retention within the probe, thereby desirably providing the capability of accurate solid mass and/or amount delivery. The compression also advantageously substantially prevents and/or mitigates the possibility of sample fall-out from the probe.

The extent of compression is variable by the amount of motion exerted by the plunger drive. This compression force, in some embodiments, can also be measured by a suitable means (such as a force strain gauge or a pressure sensor) in order to compress to a known and/or controlled pressure (or force).

• Provisional Patent
• Utility Patent

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